1. Field of the Invention
The present invention relates to the acquisition and processing of analog waveforms or signals, and more specifically to novel applications of “Signal Advance” to significantly reduce or eliminate the inherent delay in analog waveform or signal detection and acquisition.
2. Background Information
Instrumentation relies on the detection, acquisition and processing of analog signals or waveforms. The process of acquiring analog signals or waveforms typically involves detection through an analog signal transducer, amplification, conversion (including, but not limited to, analog-to-digital conversion) and subsequent signal processing, which may include spectral decomposition and typically, signal or data output, for display or control purposes.
Signal detection and processing delays are necessarily inherent in the electronic systems performing these functions. These delays adversely impact the subsequent use of the acquired signal or processed data based on the acquired signal or waveform, as the physical phenomenon underlying the generation of the analog signals may continue to vary or subside during the period that the signal is being detected, acquired and processed. Any control or intervention necessarily relies on, and in some cases reinforces, or attempts to intervene in underlying events that have transpired, and control, treatment or intervention may be less effective.
Because of these analog signal processing delays, there is no reliable way for any response output to control, intervene, treat or respond through constructive or destructive interference with the underlying phenomenon directly. In essence, any such response is to something that, quite literally, is already complete and in the past.
Current instrumentation used in these control, interventional, therapeutic or other related applications typically act to adjust response output parameters based on extrapolations made from recently acquired data. However, this instrumentation remains unable to reliably instigate a true, real-time response, as there is no way to control the timing of the applied stimulation signal to ensure the appropriately-needed constructive or destructive interference with the phenomenon underlying the generation of the detected analog signal or waveform. Analog signal or waveform conversion speed, which is critical to effective response intervention treatment or control in general, could be greatly improved by the early or “pre-” detection of these analog signals or by elimination or significant reduction of the analog signal or waveform detection and processing delays. The application of “Signal Advance” amplification to the detection of analog signals or waveforms could significantly enhance system response time.
A number of patents and patent applications, as well as, scientific publications discuss Negative Group Delay (“NGD”).
U.S. Pat. No. 5,291,156, issued to Arntz on Mar. 1, 1994, is entitled “Method and apparatus for imparting positive phase slope to a narrowband signal.” It describes a method and apparatus for imparting a positive phase slope (i.e., a negative group delay) to narrowband signals: it adjusts the phases of the various frequency components of a signal in a manner opposite to that of a delay line. The invention also permits the amount of phase slope to be adjusted, electronically, without the need for electro-mechanical apparatus or the interchange of cables. The amount of phase slope imparted to the signal can be adjusted by varying the gain (or attenuation) of the respective gain control blocks. As such, the '156 patent relates to the separation of a signal into two paths. The first one has a positive delay and thus a negative phase slope. The second is a parallel path and uses negative group delay circuitry to impart a positive phase shift, which can compensate for the positive delay of the first path.
U.S. Patent Application No. 20050127996, published for Jelonnek et al. on Jun. 16, 2005, is entitled “Arrangement for reducing non-linear distortions in an output signal of an amplifier stage.” This patent application describes a system for the reduction of non-linear signal distortion, which incorporates a negative group delay transmission device to compensate for transmission delay associated with signal distortion detection in order to generate an error signal that is added to the original signal to reduce the distortion in the original signal via a parallel signal pathway for the signal distortion. This patent application describes a system for distortion reduction related to amplification based on the “Feed-Forward principle”. It is used to reduce delays associated with the conversation of analog signals to digital signals using a predictive negative delay amplifier stage in the original signal detection/transmission path via the use of a negative group delay device in a parallel signal path which is later recombined with the original signal propagating through the main signal pathway.
Other references, e.g., U.S. Pat. No. 6,456,950 entitled “Method and apparatus for estimating and digitizing instantaneous frequency and phase of bandpass signals” and U.S. Pat. No. 6,587,064 entitled “Signal processor with local signal behavior and predictive capability”, may incorporate early or “predictive” information about the input signal characteristics, but none incorporates a “Signal Advance” amplifier.
Other seemingly-related patents (e.g., U.S. Pat. Nos. 6,466,604, 6,222,673, 6,081,379 and 4,853,933) relate to the negative group delay phenomenon applied to lasers and characteristics of varying configurations of radiation generating cavities. However, they have no relationship to the application described in the present invention, which applies the negative group delay phenomenon by using operational amplifier-based “Signal Advance” amplification to analog signal/waveform detection and processing in spectral ranges well below those described the aforementioned patents.
Also, other seemingly-related patents (e.g., U.S. Pat. Nos. 5,945,861 and 6,154,079) relate to the use of a negative delay circuit to offset delays in clock signals and prevention of a multi-locking phenomenon related to such clock cycles. However, these applications involve clock pulses and not generalized analog signals and act to offset clock signal delays and not to temporally advance analog signal/waveform detection. Therefore, these groups of patents and similar ones have no relationship to the application of negative delay amplification to an electro-physiological interface to enhance signal detection/processing response, as in the repent invention.
While these earlier teachings may fulfill their respective, particular objectives and requirements, no one has to date proposed an analog signal or waveform detection, acquisition and processing system that provides advance or “early detection” of incoming analog waveform peaks and propagates the waveform to the data acquisition system in advance of the complete detection of the actual incoming signal or waveform.